On Sun, May 12, 2013 at 06:13:34PM +0200, Bjørn Mork wrote:
> "Paul E. McKenney" <[email protected]> writes:
>
> > We don't want to back out the RCU_FAST_NO_HZ changes due to their
> > energy-efficiency benefits.
>
> Yes, that's what I assumed. Just didn't know where to start dissecting
> it...
>
> > So could you please try out Borislav's
> > patch below? He ran into the same issue a few weeks ago, and this
> > one fixed it for him.
> >
> > Thanx, Paul
> >
> > ------------------------------------------------------------------------
> >
> > rcu: Expedite grace periods during suspend/resume
> >
> > CONFIG_RCU_FAST_NO_HZ can increase grace-period durations by up to
> > a factor of four, which can result in long suspend and resume times.
> > Thus, this commit temporarily switches to expedited grace periods when
> > suspending the box and return to normal settings when resuming.
> >
> > Signed-off-by: Borislav Petkov <[email protected]>
> > Signed-off-by: Paul E. McKenney <[email protected]>
> >
> > diff --git a/kernel/rcutree.c b/kernel/rcutree.c
> > index a9610d1..d9604a4 100644
> > --- a/kernel/rcutree.c
> > +++ b/kernel/rcutree.c
> > @@ -53,6 +53,7 @@
> > #include <linux/delay.h>
> > #include <linux/stop_machine.h>
> > #include <linux/random.h>
> > +#include <linux/suspend.h>
> >
> > #include "rcutree.h"
> > #include <trace/events/rcu.h>
> > @@ -3003,6 +3004,22 @@ static int __cpuinit rcu_cpu_notify(struct
> > notifier_block *self,
> > return NOTIFY_OK;
> > }
> >
> > +static int rcu_pm_notify(struct notifier_block *self,
> > + unsigned long action, void *hcpu)
> > +{
> > + switch (action) {
> > + case PM_HIBERNATION_PREPARE:
> > + rcu_expedited = 1;
> > + break;
> > + case PM_POST_RESTORE:
> > + rcu_expedited = 0;
> > + break;
> > + default:
> > + break;
> > + }
> > + return NOTIFY_OK;
> > +}
> > +
> > /*
> > * Spawn the kthread that handles this RCU flavor's grace periods.
> > */
> > @@ -3243,6 +3260,7 @@ void __init rcu_init(void)
> > * or the scheduler are operational.
> > */
> > cpu_notifier(rcu_cpu_notify, 0);
> > + pm_notifier(rcu_pm_notify, 0);
> > for_each_online_cpu(cpu)
> > rcu_cpu_notify(NULL, CPU_UP_PREPARE, (void *)(long)cpu);
> > }
>
>
> Thanks! This patch did not make any difference for me by itself, for
> pretty obvious reasons (I didn't time restore from hibernate - only from
> suspend). But it pointed me in the right direction. Applying the
> attached patch on top of that one fixed the problem.
>
> Note that I'm also changing the restore from hibernate hook. According
> to Documentation/power/notifiers.txt :
>
> PM_POST_RESTORE An error occurred during restore from hibernation.
> Device drivers' restore callbacks have been executed
> and tasks have been thawed.
>
>
> I believe Borislav must have meant
>
> PM_POST_HIBERNATION The system memory state has been restored from a
> hibernation image or an error occurred during
> hibernation. Device drivers' restore callbacks have
> been executed and tasks have been thawed.
>
> in the above patch?
>
> Please include some combination of these patches in your upcoming v3.10
> fixes. Thanks.
I have queued the following patch, thank you, Bjørn!
Thanx, Paul
> Bjørn
>
> >From cf169d21274911fea4b6a89a0a2c7b370d9de441 Mon Sep 17 00:00:00 2001
> From: =?UTF-8?q?Bj=C3=B8rn=20Mork?= <[email protected]>
> Date: Sun, 12 May 2013 17:51:10 +0200
> Subject: [PATCH] rcu: Really switch to expedited grace periods for suspend
> MIME-Version: 1.0
> Content-Type: text/plain; charset=UTF-8
> Content-Transfer-Encoding: 8bit
>
> commit 587ff2cf ("rcu: Expedite grace periods during suspend/resume")
> enabled expedited grace periods for hibernation, but not for suspend.
> The same issue applies to both cases, so apply the same logic.
>
> Restoring on post hibernation and post suspend, but not on post
> restore, which only applies to the restore error case.
>
> Cc: Borislav Petkov <[email protected]>
> Signed-off-by: Bjørn Mork <[email protected]>
> ---
> kernel/rcutree.c | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/kernel/rcutree.c b/kernel/rcutree.c
> index 6934238..2dcbf84 100644
> --- a/kernel/rcutree.c
> +++ b/kernel/rcutree.c
> @@ -3103,9 +3103,11 @@ static int rcu_pm_notify(struct notifier_block *self,
> {
> switch (action) {
> case PM_HIBERNATION_PREPARE:
> + case PM_SUSPEND_PREPARE:
> rcu_expedited = 1;
> break;
> - case PM_POST_RESTORE:
> + case PM_POST_HIBERNATION:
> + case PM_POST_SUSPEND:
> rcu_expedited = 0;
> break;
> default:
> --
> 1.7.10.4
>
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [email protected]
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
