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Message-ID: <20071120225246.GA24380@elte.hu>
Date: Tue, 20 Nov 2007 23:52:46 +0100
From: Ingo Molnar <mingo@...e.hu>
To: Thomas Gleixner <tglx@...utronix.de>
Cc: Pavel Machek <pavel@....cz>,
kernel list <linux-kernel@...r.kernel.org>
Subject: Re: nohz and strange sleep latencies
* Thomas Gleixner <tglx@...utronix.de> wrote:
> On Tue, 20 Nov 2007, Ingo Molnar wrote:
> >
> > * Pavel Machek <pavel@....cz> wrote:
> >
> > > > and send us the output? (Enabling CONFIG_TIMER_STATS,
> > > > CONFIG_SCHED_DEBUG and CONFIG_SCHEDSTATS would maximize the amount
> > > > of information.)
> > >
> > > This was w/o hpet=disable . Do you want me to test with hpet=disable?
> >
> > no, this is fine. You've got a hpet clockevents driver and two lapic
> > drivers:
> >
> > Clock Event Device: hpet
> > set_next_event: hpet_legacy_next_event
> > set_mode: hpet_legacy_set_mode
> > event_handler: tick_handle_oneshot_broadcast
> >
> > Clock Event Device: lapic
> > set_next_event: lapic_next_event
> > set_mode: lapic_timer_setup
> > event_handler: hrtimer_interrupt
> >
> > Clock Event Device: lapic
> > set_next_event: lapic_next_event
> > set_mode: lapic_timer_setup
> > event_handler: hrtimer_interrupt
> >
> > to me this has the feeling of lapic breakage in C2 mode. Does it get any
> > better if you boot with 'nolapic'? (but that might in turn turn off
> > high-res timers and nohz in essence) Thomas, any ideas?
>
> Hmm, lapic is considered unstable in c2 by default. You have to tell
> the kernel that you trust it in C2 on the command line.
yeah, i was wondering about that too. ACPI enumerated them properly at a
certain stage:
ACPI: CPU0 (power states: C1[C1] C2[C2] C3[C3])
ACPI: CPU1 (power states: C1[C1] C2[C2] C3[C3])
but perhaps somehow we miss this fact and fail to turn off the lapic
clockevents drivers?
Ingo
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