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

[Mark Lord <lkml@rtr.ca>]

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@intel.com>
>>
>> ---
>>  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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