Re: 2.6.25 regression: powertop says 120K wakeups/sec

[Mark Lord]

Rafael J. Wysocki wrote:
> On Friday, 28 of March 2008, Venki Pallipadi wrote:
> > On Fri, Mar 28, 2008 at 03:09:22PM -0700, David Brownell wrote:
> > > On Friday 28 March 2008, Pallipadi, Venkatesh wrote:
> > > > You should have a dmesg line which looks like
> > > > ACPI: CPU0 (power states: C1[C1] C2[C2]
> > > > Do you see C2 in such line?
> > > Yes:
> > >
> > > ACPI: CPU0 (power states: C1[C1] C2[C2])
> >
> > David,
> >
> > I think I figured out the bug...
> >
> > Can you try the below patch and confirm that it works (over upstream - ignore
> > the earlier revert patch I sent to you).
> >
> > Thanks,
> > Venki
> >
> > ----
> >
> >
> > Patch to fix huge number of wakeups reported due to recent changes in
> > processor_idle.c. The problem was that the entry_method determination was
> > broken due to one of the recent commits (bc71bec91f987) causing
> > C1 entry to not to go to halt. This should also fix the hang reported here.
> > http://bugzilla.kernel.org/show_bug.cgi?id=10093
>
> Ah, thanks for figuring that out.  As a regression fix, it should go upstream
> ASAP, I think.
..

Would this have any applicability to 2.6.24 as well?

I have seen/reported a similar bug there many times in the past,
with no resolution.  There's even a bugzilla entry for it somewhere.
???


> > Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@xxxxxxxxx>
> >
> > ---
> >  drivers/acpi/processor_idle.c |    4 ++++
> >  1 file changed, 4 insertions(+)
> >
> > Index: linux-2.6/drivers/acpi/processor_idle.c
> > ===================================================================
> > --- linux-2.6.orig/drivers/acpi/processor_idle.c	2008-03-28 15:31:13.000000000 -0700
> > +++ linux-2.6/drivers/acpi/processor_idle.c	2008-03-28 15:40:50.000000000 -0700
> > @@ -848,6 +848,7 @@ static int acpi_processor_get_power_info
> >  		/* all processors need to support C1 */
> >  		pr->power.states[ACPI_STATE_C1].type = ACPI_STATE_C1;
> >  		pr->power.states[ACPI_STATE_C1].valid = 1;
> > +		pr->power.states[ACPI_STATE_C1].entry_method = ACPI_CSTATE_HALT;
> >  	}
> >  	/* the C0 state only exists as a filler in our array */
> >  	pr->power.states[ACPI_STATE_C0].valid = 1;
> > @@ -960,6 +961,9 @@ static int acpi_processor_get_power_info
> >  				 cx.address);
> >  		}
> >  
> > +		if (cx.type == ACPI_STATE_C1) {
> > +			cx.valid = 1;
> > +		}
> >  
> >  		obj = &(element->package.elements[2]);
> >  		if (obj->type != ACPI_TYPE_INTEGER)
> --
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