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SubjectRe: Performance/resume issues on Toshiba NB305
On Fri, 25 Feb 2011, Seth Forshee wrote:
> On Fri, Feb 25, 2011 at 09:37:39PM +0100, Thomas Gleixner wrote:
> > On Fri, 25 Feb 2011, Seth Forshee wrote:
> > That seems to be related to low power states. When the machine goes
> > idle we switch into lower power states and that requires to use the
> > hpet instead of the local apic timer as that one stops.
> >
> > You could verify that theory by booting with processor.max_cstate=1
>
> This fixes the performance in combination with intel_idle.max_cstate=0.
> Alternately, intel_idle.max_cstate=1 works. But the resume still hangs.

That was expected :)

> Is the answer to quirk the machine to avoid deep C-states, or is there
> some better way I can fix this?

Let's wait for the intel and acpi folks. It would be interesting what
the new intel toy says to your BIOS.

http://biosbits.org/

> > > +unlock:
> > > raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);
> > > }
> >
> > Why would you need that? We should not call that when the broadcast
> > device does not have TICKDEV_MODE_ONESHOT. If we do the bug is
> > somewhere else.
>
> Then there must be a bug. When I cleared CLOCK_EVT_FEAT_ONESHOT for the
> HPET without this change the HPET got put into oneshot mode. The local
> tick device is checked before switching to nohz, but not the broadcast
> device. This change was just a quick hack to get around that and test my
> theory.

Indeed. The patch below should cure that.

Thanks,

tglx

----------->
Subject: clockevents-fix-broadcast.patch
From: Thomas Gleixner <tglx@linutronix.de>
Date: Fri, 25 Feb 2011 22:34:23 +0100
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
kernel/time/tick-broadcast.c | 10 ++++++++++
kernel/time/tick-common.c | 6 +++++-
kernel/time/tick-internal.h | 3 +++
3 files changed, 18 insertions(+), 1 deletion(-)
Index: linux-2.6/kernel/time/tick-broadcast.c
===================================================================
--- linux-2.6.orig/kernel/time/tick-broadcast.c
+++ linux-2.6/kernel/time/tick-broadcast.c
@@ -600,4 +600,14 @@ int tick_broadcast_oneshot_active(void)
return tick_broadcast_device.mode == TICKDEV_MODE_ONESHOT;
}

+/*
+ * Check whether the broadcast device supports oneshot.
+ */
+bool tick_broadcast_oneshot_available(void)
+{
+ struct clock_event_device *bc = tick_broadcast_device.evtdev;
+
+ return bc ? bc->features & CLOCK_EVT_FEAT_ONESHOT : false;
+}
+
#endif
Index: linux-2.6/kernel/time/tick-common.c
===================================================================
--- linux-2.6.orig/kernel/time/tick-common.c
+++ linux-2.6/kernel/time/tick-common.c
@@ -51,7 +51,11 @@ int tick_is_oneshot_available(void)
{
struct clock_event_device *dev = __this_cpu_read(tick_cpu_device.evtdev);

- return dev && (dev->features & CLOCK_EVT_FEAT_ONESHOT);
+ if (!dev || !(dev->features & CLOCK_EVT_FEAT_ONESHOT))
+ return 0;
+ if (!(dev->features & CLOCK_EVT_FEAT_C3STOP))
+ return 1;
+ return tick_broadcast_oneshot_available();
}

/*
Index: linux-2.6/kernel/time/tick-internal.h
===================================================================
--- linux-2.6.orig/kernel/time/tick-internal.h
+++ linux-2.6/kernel/time/tick-internal.h
@@ -36,6 +36,7 @@ extern void tick_shutdown_broadcast_ones
extern int tick_resume_broadcast_oneshot(struct clock_event_device *bc);
extern int tick_broadcast_oneshot_active(void);
extern void tick_check_oneshot_broadcast(int cpu);
+bool tick_broadcast_oneshot_available(void);
# else /* BROADCAST */
static inline void tick_broadcast_setup_oneshot(struct clock_event_device *bc)
{
@@ -46,6 +47,7 @@ static inline void tick_broadcast_switch
static inline void tick_shutdown_broadcast_oneshot(unsigned int *cpup) { }
static inline int tick_broadcast_oneshot_active(void) { return 0; }
static inline void tick_check_oneshot_broadcast(int cpu) { }
+static inline bool tick_broadcast_oneshot_available(void) { return true; }
# endif /* !BROADCAST */

#else /* !ONESHOT */
@@ -76,6 +78,7 @@ static inline int tick_resume_broadcast_
return 0;
}
static inline int tick_broadcast_oneshot_active(void) { return 0; }
+static inline bool tick_broadcast_oneshot_available(void) { return true; }
#endif /* !TICK_ONESHOT */

/*


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