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SubjectRe: Tracing of power:power_start events doesn't work
On 12/05/2010 10:57, Robert Schöne wrote:
> On Wed, den 05.05.2010-05-05, 07:33 -0700 schrieb Arjan van de Ven:
>
>> On 5/5/2010 7:31, Steven Rostedt wrote:
>>
>>> On Wed, 2010-05-05 at 16:11 +0200, Ronny Tsch�ter wrote:
>>>
>>>
>>>> /*
>>>> * Include the apic definitions for x86 to have the APIC timer related
>>>> defines
>>>> @@ -796,6 +797,18 @@ static int acpi_idle_bm_check(void)
>>>> */
>>>> static inline void acpi_idle_do_entry(struct acpi_processor_cx *cx)
>>>> {
>>>> + switch (cx->type) {
>>>> + case ACPI_STATE_C1:
>>>> + trace_power_start(POWER_CSTATE, 1);
>>>> + break;
>>>> + case ACPI_STATE_C2:
>>>> + trace_power_start(POWER_CSTATE, 2);
>>>> + break;
>>>> + case ACPI_STATE_C3:
>>>> + trace_power_start(POWER_CSTATE, 3);
>>>> + break;
>>>> + }
>>>> +
>>>>
>>> Depending on gcc, the above can bloat the code since each call to
>>> trace_power_start() is a macro expanded. Try to call it just once.
>>> Perhaps one of the following:
>>>
>> the code is also incorrect fundamentally.
>> You need to pass in the mwait value or equivalent; the ACPI STATE type is
>> pretty much useless random garbage and should completely be ignored.
>>
> You're correct for your case (switching to c-state via monitor/mwait).
> But the current implementation is broken too. It works only if your
> kernel uses processor_idle AND monitor/mwait. For all other cases it
> fails - may it be on Ronnys system, that uses IO port based C-states or
> my system, that uses cpu_idle (not processor_idle).
>
> I'd suggest, that it should work for IO port based switches and could be
> included in the syntactic block of that case.
> Afaik, halt means that the processor goes to C1. So in this block, there
> could be a power_start event too with 1 as new state. (Maybe there are
> problems with AMDs C1E which would be reported as C1.)
>
> Robert
>
Unfortunately the bug still exists in kernel 2.6.34. On my system I'm
not able to trace power:power_start events, because they are not
reported. Regarding to the preceding comments I moved my code snippet
into the IO port based C-state part of acpi_idle_do_entry(). Therefore
it should not interfere with the other two C-state calls in this function.
Furthermore a lot of other code sequences in processor_idle.c use the
ACPI STATE type in if- or switch-statements. So I don't think that ACPI
STATE type is useless garbage.

Finally here is my new patch:


diff --git a/old/processor_idle.c b/new/processor_idle.c
index 5939e7f..5818522 100644
--- a/old/processor_idle.c
+++ b/new/processor_idle.c
@@ -43,6 +43,7 @@
#include <linux/clockchips.h>
#include <linux/cpuidle.h>
#include <linux/irqflags.h>
+#include <trace/events/power.h>

/*
* Include the apic definitions for x86 to have the APIC timer related
defines
@@ -807,6 +808,10 @@ static inline void acpi_idle_do_entry(struct
acpi_processor_cx *cx)
} else {
int unused;
/* IO port based C-state */
+ trace_power_start(POWER_CSTATE,
+ cx->type == ACPI_STATE_C1 ? 1 :
+ cx->type == ACPI_STATE_C2 ? 2 :
+ 3);
inb(cx->address);
/* Dummy wait op - must do something useless after P_LVL2 read
because chipsets cannot guarantee that STPCLK# signal
--
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