Re: [pytimechart] new cpuidle tracepoint

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Hi Pierre,

On Mon, Feb 28, 2011 at 4:09 PM, Pierre Tardy <tardyp@xxxxxxxxx> wrote:
> On Mon, Feb 28, 2011 at 2:43 PM, Vincent Guittot
> <vincent.guittot@xxxxxxxxxx> wrote:
>> On 27 February 2011 17:31, Pierre Tardy <tardyp@xxxxxxxxx> wrote:
>>> On Fri, Feb 18, 2011 at 11:03 AM, Vincent Guittot
>>> <vincent.guittot@xxxxxxxxxx> wrote:
>>>> Hi,
>>>> I have started to use the new cpuidle tracepoint and created a plugin
>>>> for pytimechart.
>>>> I'm not sure if it's the right way to add this cpuidle trace format
>>>> update but it's the less intrusive one.
>>> Yes, it is okay. I actually plan to also put the whole cpuidle trace
>>> handling into such plugin.
>>> Would you care to send me one of your trace file, so that I can
>>> actually test it.
>> Yes, I have attached the trace file which is Vishwa's one in fact.
> Thanks, I applied and pushed the patch.
> Please note that your trace has some suspicious tracepoints with same
> timestamps for end of cpuidle and start of next cpuidle.
That comes from a known problem about the timer on OMAP. The 32K timer
is feeding the trace timestamps and so the granularity is not high
enough (30us).

> <idle>-0     [000]   270.645935: cpu_idle: state=2 cpu_id=0
> <idle>-0     [000]   271.020935: cpu_idle: state=4294967295 cpu_id=0
> <idle>-0     [000]   271.020935: cpu_idle: state=2 cpu_id=0
> <idle>-0     [000]   271.036560: cpu_idle: state=4294967295 cpu_id=0
> <idle>-0     [000]   271.073395: cpu_idle: state=1 cpu_id=0
> Also, cpuidle states name in pytimechart are very selfishly hardcoded
> with intel's convention.
> Can you tell what is your convention, so that we can think of a best
> way to handle display of state's name for ftrace text output?
The power trace points API is described in Documentation/trace/events-power.txt.

Here is an excerpt of it:
The value of '-1' or '4294967295' for state means an exit from the
current state,
i.e. trace_cpu_idle(4, smp_processor_id()) means that the system
enters the idle state 4, while trace_cpu_idle(PWR_EVENT_EXIT,
means that the system exits the previous idle state.

The event which has 'state=4294967295' in the trace is very important
to the user
space tools which are using it to detect the end of the current state, and so to
correctly draw the states diagrams and to calculate accurate statistics etc.

I would be glad to help on pytimechart, please let me know!


> Regards,
> Pierre
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