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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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