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Bug#521944: linux-image-2.6.29-1-686: Excessive number of interrupts from hrtimer_start_expires



On Tue, Feb 16, 2010 at 04:46:31AM +0000, Ben Hutchings wrote:
> On Sat, 2010-02-06 at 09:31 +0000, Tom Parker wrote:
> > On 2 February 2010 21:16, maximilian attems <max@stro.at> wrote:
> > > Squeeze will release with 2.6.32 can anyone of you still
> > > reproduce this?
> > >
> > > also please make sure to use latest powertop, aka
> > > ii  powertop       1.13~pre201001 Linux tool to find out what is using power
> > 
> > palfrey@drone:[~] dpkg -l |grep powertop
> > ii  powertop                                      1.13~pre20100125-1
> >                             Linux tool to find out what is using power
> > o
> > palfrey@drone:[~] uname -a
> > Linux drone 2.6.32-1-686 #1 SMP Mon Feb 1 01:37:26 UTC 2010 i686 GNU/Linux
> > 
> > Attached is powertop.log ('powertop -d') and top.log('top -b -n 1')
> > 
> > As you can see, the major wakeup is still "Load balancing tick", which
> > I'm guessing is a translated name for hrtimer_start_expires? I think
> > the ACPI estimate of 1.1W is a little off though...
> 
> hrtimer_start_expires() is a generic function in the kernel to schedule
> a wakeup by the high-resolution timer.  In 2.6.32 it is an inline
> function that calls hrtimer_start_range_ns().  Powertop recognises and
> relabels some specific calling sequences, including this one.
> 
> If I understand correctly, these are scheduler ticks that periodically
> interrupt the running task (preemption).  However, on a kernel compiled
> with the NOHZ option (as Debian's kernel images are) this should never
> wake the system up - scheduler ticks are disabled when there are no
> tasks ready to run and no other timers due to expire before the next
> tick.
> 
> I can only suggest you report this upstream at
> <http://bugzilla.kernel.org>.  Use product 'Process Management',
> component 'Scheduler'.  Let us know the bug number so we can track it.

Did you report this at http://bugzilla.kernel.org ?

Cheers,
        Moritz



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