linux-kernel - Re: high power consumption in recent kernels

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Date:	Thu, 08 Jul 2010 13:58:23 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Arjan van de Ven <arjan@...radead.org>
Cc:	Norbert Preining <preining@...ic.at>, linux-kernel@...r.kernel.org,
	Ingo Molnar <mingo@...e.hu>, akpm <akpm@...ux-foundation.org>
Subject: Re: high power consumption in recent kernels

On Thu, 2010-07-08 at 04:57 -0700, Arjan van de Ven wrote:
> On Thu, 08 Jul 2010 11:06:32 +0200
> Peter Zijlstra <peterz@...radead.org> wrote:
> 
> > On Wed, 2010-07-07 at 01:45 +0900, Norbert Preining wrote:
> > 
> > > it seems that some of the (?)recent(?) changes have increased the
> > > power consumption of my note book considerably.
> > > 
> > > First of all, running powertop with normal programs started, but 
> > > doing nothing, I am still at 14W while I could go down to 9W before
> > > (but the 9W was with dimmed display).
> > > 
> > > In the list of top causes for wakeup I have
> > > Top causes for wakeups:
> > >   34.2% (185.3)   [kernel scheduler] Load balancing tick
> > >   23.9% (129.6)   [extra timer interrupt]
> > >   10.8% ( 58.6)   firefox-bin
> > >    9.2% ( 49.7)   [iwlagn] <interrupt>
> > >    7.2% ( 39.1)   [kernel core] hrtimer_start (tick_sched_timer)
> > >    3.9% ( 20.9)   PS/2 keyboard/mouse/touchpad interrupt
> > > which show one new thing to me I haven't seen before, the Loa
> > > balancing tick.
> > 
> > I think that is what powertop calls our regular tick (Arjan?), and as
> 
> it's "hrtimer_start_range_ns (tick_sched_timer)" if it's done by the
> idle thread.
> 

then wth is "[kernel scheduler] load balancing tick"?
and for that matter, what is "[extra timer interrupt]", surely the timer
hardware doesn't generate spurious interrupts?
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